Altruism can evolve when relatedness is low: Evidence from bacteria committing suicide upon phage infection Journal Article


Author(s): Refardt, Dominik; Bergmiller, Tobias; Kümmerli, Rolf
Article Title: Altruism can evolve when relatedness is low: Evidence from bacteria committing suicide upon phage infection
Affiliation IST Austria
Abstract: High relatedness among interacting individuals has generally been considered a precondition for the evolution of altruism. However, kin-selection theory also predicts the evolution of altruism when relatedness is low, as long as the cost of the altruistic act is minor compared with its benefit. Here, we demonstrate evidence for a low-cost altruistic act in bacteria. We investigated Escherichia coli responding to the attack of an obligately lytic phage by committing suicide in order to prevent parasite transmission to nearby relatives. We found that bacterial suicide provides large benefits to survivors at marginal costs to committers. The cost of suicide was low, because infected cells are moribund, rapidly dying upon phage infection, such that no more opportunity for reproduction remains. As a consequence of its marginal cost, host suicide was selectively favoured even when relatedness between committers and survivors approached zero. Altogether, our findings demonstrate that low-cost suicide can evolve with ease, represents an effective host-defence strategy, and seems to be widespread among microbes. Moreover, low-cost suicide might also occur in higher organisms as exemplified by infected social insect workers leaving the colony to die in isolation.
Keywords: Hamilton's rule; Kin selection; Altruistic suicide; Host defence; Parasite transmission; Structured population
Journal Title: Proceedings of the Royal Society of London Series B Biological Sciences
Volume: 280
Issue 1759
ISSN: 0962-8452
Publisher: Royal Society, The  
Date Published: 2013-01-01
Sponsor: This work was supported by the Competence Center Environment and Sustainability of the ETH (to D.R.), the Swiss National Science Foundation, and the European Commission (to R.K.).
URL:
DOI: 10.1098/rspb.2012.3035
Notes: We thank John W. Little, Ing-Nang Wang, Benjamin Kerr, Bärbel Stecher, Martin Ackermann and Winfried Boos for providing bacteria and phage strains, the flow cytometry laboratory at the ETH Zürich, Anette Schütz and Olin Silander for help with flow cytometry, and Jim Bull, Tim Cooper, Fred Inglis, Laurent Keller, Stu West and an anonymous reviewer for valuable comments.
Open access: yes (repository)